Manufacture of concrete pipes

ABSTRACT

IN AN APPARATUS FOR MANUFACTURING REINFORCED CONCRETE PIPE, THE IMPROVEMENT WHEREBY THE RETARDING TANGENTIAL FORCE EXERTED BETWEEN THE COMPACTING ROLLER AND THE PIPE IS SUBSTANTIALLY OVERCOME. THE MEANS FOR OVERCOMING THE RETARDING FORCE INCLUDES MOTOR MEANS OPERATIVELY CON-   NECTED TO DRIVE THE COMPACTING ROLLER AND MOTOR MEANS OPERATIVELY AND CONTROLLABLY CONNECTED TO DRIVE THE PIPE.

June 22, 1971 C. A. BAKER L MANUFACTURE OF CONCRETE PIPES 4 Sheets-Sheet 1 Filed March 14. 1969 June 1971 c. A. BAKER E L MANUFACTURE OF CONCRETE PIPES 4 Sheets-Sheet 2 POWER PACK FIG.6

RECTIFIER POWER RECTIFIER June 22, 1971 C. A. BAKER ET AL MANUFACTURE OF CONCRETE PIPES 4 Sheets-Sheet 3 Filed March 14, 1969 FIG.8

June 22, 1971 c. A. BAKER ETAL 3,585,694

MANUFACTURE OF CONCRETE PIPES Filed March 14, 1969 4 Sheets-Sheet 4.

h v l I .L 1. POWER PACK E United States Patent, M

Int. Cl. B28b 21 /24 U.S. Cl. 25--30C 8 Claims ABSTRACT OF THE DISCLOSURE In an apparatus for manufacturing reinforced concrete pipe, the improvement whereby the retarding tangential force exerted between the compacting roller and the pipe is substantially overcome. The means for overcoming the retarding force includes motor means operatively connected to drive the compacting roller and motor means operatively and controllably connected to drive the pipe.

This application is a continuation-in-part of US. application Ser. No. 567,272 filed July 22, 1966 and now abandoned.

The present invention relates to apparatus for the manufacture of pipes of reinforced concrete or the like and more particularly to the type of machine wherein a hollow mould is supported on four or more spaced revolving discs and spun about its longitudinal axis at a speed great enough for the centrifugal effect to prevent the falling of pipe material placed in the said mould, the said material being compacted by a revolving roller mounted inside the said mould with its axis parallel to but sufficiently eccentric with respect to the axis of the said mould to produce the pipe wall thickness required.

It is customary in such machines to allow the roller which presses on the concrete to idle, being driven by a tangential component of the resultant force acting between the roller and the concrete. This tangential com ponent of force may be of considerable magnitude and if the pipe wall is being formed around a reinforcing cage of wire, rod or mesh the shearing of the plastic concrete induced by the tangential component force may cause the destruction of such reinforcement. Similarly the reinforcement may be distored or twisted so rendering the pipe unfit for further processing. Thus for example if the power required to drive the roller against rolling friction is 50 HF. and the surface speed of the roller is 1500 feet per minute the tangential component of force developed is given by The present invention has for its primary object to provide the means whereby the above described tangential force may be eliminated, minimised, or controlled at will so that the disadvantages above described are either eliminated or considerably reduced.

In the drawings:

FIG. 1 is a side elevational view of a first embodiment of a centrifugal pipe making machine with roller compaction according to the present invention.

FIG. 2 is a part sectional elevation of the mould and related parts of the machine.

FIG. 3 is a part end elevation showing details of the roller suspension.

FIG. 4 is a circuit diagram of the roller handling and loading hydraulic system.

3,585,694 Patented June 22,, 1971 FIG. 5 is a block diagram of the connection of load cells to a balancing box and force indictaing galvanometer.

FIG. 6 is a block diagram of the connection to a torque controlled electric motor.

FIG. 7 is a block diagram of the interconnection of a force indicating system to a controlled rectifier converter supplying a motor.

FIG. 8 is a sectioned end elevation of a second embodiment of a centrifugal pipe making machine with roller compaction according to the present invention.

FIG. 9 is a side elevation of the second embodiment machine.

FIG. 10 is a circuit diagram of the roller handling and loading hydraulic system of the second embodiment machine.

Referring to the drawings and to the numerals of reference thereon the first embodiment machine illustrated consists of base members 1 which support bearings 2 which carry shafts 3 and 4. Both shafts have discs 9 fixed at their ends and these discs support the pipe mould which typically consists of mould end rings 51 and 52 and mould case 53.

The pipe in the mould is made up of concrete 55 and reinforcement cage 54.

The roller 10 with integral journals 13 is rotatably supported in anti-friction cartridge bearings 11 which are de-moutably carried in hinged clamps 12 on side rails 17.

Double acting hydraulic cylinders 23 are trunnion mounted on supporting bases 25 and have piston rods 24 which are fixedly connected to side rails 17.

Aligned with each side rail a rigidly mounted post 21 locates a slider 20 which is free to slide vertically without rotation about the post 21. Rods 19 fixedly secured to the ends of the side rails 17 enter freely fitting holes in the slider 20 and thus each slider 20 is caused to move vertically in unison with its associated side rail 17.

Resistance strain gauge tension/compression load cells 22 are pivotally connected to sliders 20 and to side rails 17 and balance weights 18 are secured to side rails 17 at positions such that in the static condition with the roller 10 out of contact With the concrete 55 and the mould ends 51 and 52 each side rail assembly 10, 11, 12, 17, 18, 19, 20, 22, 23, 24 is in balance about the trunnion base 25 and no force exists then in the load cells 22.

The roller handling and loading hydraulic system is powered from an hydraulic power pack 26 which consists essentially of an electric motor driven pressure limited hydraulic pump and the hydraulic cylinders 23 are operated by manual control of the directional control valves 27 the maximum downward loading on the pipe 55 being limited by the setting of pressure relief valves 29 the pressure being indicated by pressure gauges 28. The roller 10' is driven by a motor 16 through universal joints 14 and Cardan shaft 15. The motor 16 may be powered by any suitable means such as electrical or hydraulic power and should have a constant speed characteristic at the chosen speed of operation. The pipe mould 51, 52, 53 is driven by motor 8 through pulleys 7 and 5 by belt 6 or equivalent means.

Referring to FIGS. 3 and 5 the two resistance strain gauge load cells 22 are battery powered from balancing box 41 which embodies bridge balancing and sensitivity controls for both load cells and a resistance network to summate the output from both load cell bridges, the total electrical output being indicated by galvanometer 42 as the total tangential force acting between the roller 10 and the pipe 55.

Referring to FIGS. 2.. and 6 a direct current shunt wound electric motor 8 is powered from a manually controlled reversible thyristor static converter 30 through ammeter 44, the motor field being supplied by a separate static rectifier 32 from the A.C. supply line and thus by controlling the output from the converter 30 the machine operator may cause the motor 8 to exert a torque in either direction of rotation and hence any desired tangential force between roller and pipe 55 may be adjusted at the control of converter and indicated at galvanometer 42. Thus if the desired force so indicated is zero the output of the converter 30 and hence the motor 8 will be adjusted to give just sufiicient power to overcome friction in bearing 2 and 3 and discs 9, the roller motor 16 then delivering exactly the torque required to overcome rolling friction between the roller 10 and pipe 55.

It is found that for minimum movement of concrete and hence minimum damage to the reinforcement cage 54 the required force indication on galvanometer 42' may vary somewhat from zero according to the pipe size, roller diameter and such variables.

The optimum force indication for a particular size of pipe maybe found experimentally and subsequently repeated at will, any variation in power to motor 8 required from time to time being adjusted manually at converter 30.

Alternatively as shown in FIG. 7 it is practicable to obtain automatic control of the power to motor 8. A direct current shunt wound motor 8 obtains its field supply from static rectifier 3-2 and its armature supply from a reversible thyristor static converter 31.

A voltage regulated direct current power supply 33 provides energisation for reference potentiometers 38 and 40 and for differential amplifiers 36, 37 and 39. Armature current feed back control is established via DC. current transformer 34 and current control amplifier 36.

Speed control of the motor 8 is established via tachometer generator 35, speed reference potentiometer 38 and speed control amplifier 37.

The load cells 22 connected to balancing box 41 and indicator 42 as described previously for FIG. 5 provide an electrical control voltage output of equivalent sign and of magnitude proportional to that of the tangential force acting on the roller 10. This control voltage is balanced against a preset torque equivalent voltage from torque control potentiometer 40 at torque control amplifier 39.

For automatic operation the speed control potentiometer 38 is set so that the motor is caused to accelerate up to a speed slightly below its uneuergised speed if the machine is driven only from the energised roll driving motor 16.

The motor then if driven at the higher speed, slightly above its tachometer controlled speed will receive no positive torque producing signal (i.e. in the direction of normal machine rotation) and can receive no negative torque producing signal on account of blocking diode 43. At the same time a torque control signal from amplifier 39 will cause the torque setting of potentiometer 40 to be satisfied by control of converter current through amplifier 36 until the torque of motor 8 is such as to result in the desired tangential force on the roller 10.

Alternatively to the use of load cells 22 as means of indicating and controlling the tangential force on the roller 10 an a'mmeter 44 connected in the armature circuit of the motor 8 will give a useful but less accurate parametric indication of the tangential force. It will be evident that a similar form of automatic control might, for example, be obtained by substituting for the shunt wound motor 8 a slip ring A.C. induction motor with forward and reverse D.C. controlled reactors in the A.C. supply.

It will also be evident that the desired operating condition with respect to the resultant tangential force between the roller and the concrete may alternatively be obtained if the roles of the constant speed characteristic motor and the controlled torque motor are interchanged.

That is to say it is alternatively possible for motor '8 to have a constant speed characteristic and for motor 16 to be controlled as shown in FIG. 7 but in general it is found that the desired operating condition is given when the power of motor 16 is much greater than the power of motor 8 so that it is more economical to control the power of motor *8.

The second embodiment machine illustrated consists of a main frame which carries two fixed portal frames 61 and two fixed brackets '65. The portal frames 61 support bearings 62 which carry shafts 63 and 72. Both shafts have discs 64 fixed at their ends and these discs engage the pipe mould end rings 51 and 52 so giving endwise constraint to the mould and resisting upthrust. Shaft 63 is driven from motor 8 via belt 6 and pulleys 7 and 5 and thus a drive is provided to the mould 51, 52, 53 via discs 64 on shaft 63. The mould 51, 52, 53 surrounds the pipe which is made up of concrete 55 and reinforcement cage 54.

Roller 80 with integral journals 83 is rotatably supported in anti-friction cartridge bearings 81 which are de-mountably carried in hinged clamps 82 on side rails 67. Double acting hydraulic cylinders 68 and 70 are trunnion mounted on main frame '60 and have piston rods 69 and 71 respectively pivotally connected to side rails 67.

Resistance strain gauge tension/compression load cells 22 are pivotally connected to cylinders 66 and to brackets 65 and thus any tangential force between roller 80 and pipe 55 is resisted from tilting cylinders 66 by the load cells 22. The roller handling and loading hydraulic system of FIG. 10 employs similar parts similarly numbered to the system described for the first embodiment machine except that cylinders 68 and 70 connected in series replace cylinders 23. The area of the cylinder 68 is twice the area of cylinder 70 and the area of the piston rod of cylinder 68 is half the area of the cylinder 68 and thus equal to the area of cylinder 70. Hence displacement of the piston of cylinder 68 will result in an equal displacement of the piston of cylinder 70* to which it is hydraulically connected and thus the associated side rail will be caused to move vertically by equal amounts at each end and so will remain horizontal at all times the roller remaining equidistant from the discs 64 on each side of the machine.

The roller 80 is driven through universal joints 14 and Cardan shaft 15 by motor 16 which is fixedly supported on the main frame 60.

Motors 8 and 16 and the power supply and control for motor -8 and the ancillary equipment for the load cells 22 for the second embodiment machine may be as for the alternative schemes described for the first embodiment machine.

While there has been described what are at present considered two preferred embodiments of the present invention it will be appreciated by those skilled in the art that various changes and modifications can be made therein without departing from the essence of the invention and it is intended to cover herein all such changes as come within the true spirit and scope of the appended claims.

Having now described our invention, what we claim as new and desire to secure by Letters Patent is:

1. Apparatus for the manufacture of a reinforced concretepipe comprising, a rotatable mould for receiving a concrete mixture and a reinforcement cage to form the pipe, a compacting roller supported for rotation on an axis parallel to the axis of the mould for compacting the concrete mixture as the pipe is formed in the mould, a first motor means for rotating the mould, a second motor means for rotating the compacting roller, and means for controlling the power output of one of said motor means so that it will develop a rotary force counter to and substantially equal to the retarding tangential force exerted between the compacting roller and the pipe as the pipe is being formed in the mould and compacted by the compacting roller.

2. Apparatus for the manufacture of a reinforced concrete pipe comprising a rotatable mould for receiving a concrete mixture and a reinforcement cage to form the pipe, a first motor means for rotating the mould so as to apply centrifugal force to the concrete mixture thereby to form the pipe, a rotatable compacting roller supported to extend longitudinally of the mould and located off centre with respect thereto to engage the inner surface of the pipe and compact the concrete mixture as the pipe is formed in the mould, a second motor means operatively connected to the compacting roller for applying a rotary force to the compacting roller, and means for controlling the power output of one of said motors so that it will develop a rotary force counter to and substantially equal to the retarding tangential force exerted on the pipe by the compacting roller as the pipe is being formed in the mould and compacted by the roller.

3. Apparatus for the manufacture of a reinforced concrete pipe comprising, a rotatable mould for receiving a concrete mixture and a reinforcement cage to form the pipe, a rotatable compacting and driving roller supported to extend longitudinally of the mould and located off centre with respect thereto for rotating the mould to apply centrifugal force to the concrete mixture thereby to form the pipe and for compacting the concrete mixture as the pipe is formed in the mould, a first motor means for rotating the compacting and driving roller, a second motor means operatively connected to the rotatable mould, and means for controlling the power output of one of said motors so that it will develop a rotary force counter to and substantially equal to the retarding tangential force exerted on the compacting and driving roller by the pipe as the pipe is being formed in the mould and compacted by the compacting and driving roller.

4. Apparatus for roller compacting a spun reinforced concrete pipe comprising, disc means for supporting and driving a hollow pipe mould containing a reinforcement cage and a concrete mixture, a first motor means for driving said disc means, a compacting roller located inside the mould and having its axis substantially parallel with the axis of the mould, a second motor means for rotating the compacting roller, means for radially loading said compacting roller against the pipe as it is being formed from the concrete mixture, means for measuring and indicating the tangential force between the pipe and the compacting roller, and means for controlling the output of one of said motor means so that the tangential force exerted between the pipe and the compacting roller is at a value such that there is minimum tangential movement of the concrete mixture in the mould as the pipe is formed thereby minimizing damage to the reinforcing cage.

5. Apparatus according to claim 4, in combination with means for automatically controlling the tangential force at a predetermined value.

6. Apparatus according to claim 4, wherein the measuring and indicating means comprises an electrical circuit incorporating load cells and the controlled motor means includes an electric motor.

7. Apparatus according to claim 4, wherein the con trol means is connected to control the first motor means.

8. Apparatus according to claim 4, wherein the control means is connected to control the second motor means.

References Cited UNITED STATES PATENTS 2,671,260 3/1954 Jessen et a1. 264-3'12X 2,722,044 11/1955 Ohanlund et a1 25-30 3,160,939 12/1964 Franklin et a1. 25-30 J. SPENCER OVERHOLSER, Primary Examiner J. S. BROWN, Assistant Examiner US. Cl. X.R. 2 643 10, 312 

